Thermal oil heater directly inserts the electric heater into an organic carrier (thermal oil) for direct heating, then circulates the heated thermal oil to the heat-using equipment through a high-temperature oil pump. The oil is returned to the electric thermal oil heater from the outlet of the heat-using equipment, completing a full-cycle heating system. The electric thermal oil heater features a digital temperature controller for precise temperature control and is equipped with over-temperature, low-oil level, and over-pressure alarm functions.